<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>IFE-Task_13</title>
  </head>
<body>

  <label>请输入北京今天空气质量：<input id="aqi-input" type="text"></label>
  <button id="button">确认填写</button>

  <div>您输入的值是：<span id="aqi-display">尚无录入</span></div>

<script type="text/javascript">

(function() {
    var btn = document.getElementById("button"),
        message = document.getElementById("aqi-input"),
        show = document.getElementById("aqi-display");

    btn.onclick = function(){
            show.innerHTML = message.value;
    }
})();

</script>
</body>
</html>